Photocell construction



Feb. 9, 1954 c. EKSTEIN PHOTOCELL CONSTRUCTION Filed March 21, 1952 FIG. I.

FIG. 2.

FIG. 3.

FIG. 5.

a my 2 W T i W ME A 5. M. 9

Patented Feb. 9, 1954 UNITED STATES i ATT OFFICE PHOTOCELL CONSTRUCTION Charles Ekstein, Brooklyn, N. Y., assignor to Vitro Corporation of America, New York, N. Y., a corporation of Delaware 9 Claims.

My invention relates to cell constructions for devices electrically responsive to radiation.

It is an object of the invention to provide an improved construction and method of construction for devices of the character indicated.

It is another object to provide a more rugged cell construction which may be less electrically sensitive to mechanical shock.

It is a further object to provide a cell construction inherently possessing greater energygathering properties than are inherent in the basic radiation-responsive element of the cell.

Other objects and various further features of novelty and invention will be pointed out or will become apparent to those skilled in the art from a reading of the following specification in conjunction with the accompanying drawings. In said drawings, which show, for illustrative purposes only, preferred forms of the invention:

Fig. 1 is an enlarged view in perspective of a cell construction incorporating features or the invention;

Fig. 2 is a vertical sectional view to illustrate a step in the construction of the assembly of Fig. 1;

Fig. 3 is an enlarged side view of the radiation-responsive element of Fig. 1 and of electrical connections thereto;

Fig. 4 is a view similar to Fig. 3 but illustrating a modification; and

Fig. 5 is a view similar to Fig. 2 and illustrating an alternative method of construction.

Briefly stated, my invention contemplates an improved construction and method of construction for radiation-responsive cells. The construction may utilize the most brittle of sensitive crystalline materials and yet be rendered relatively insensitive to mechanical shock. This is achieved bysecuring spaced electric-contact portions of the crystal to enlarged fiat-headed ends of electric-terminal members over the flat areas thereof; and by casting the assembly in a body of plastic material transparent to the radiation. The energy-gathering properties of the complete assembly may be greatly enhanced by so contouring a substantial external area or" the body as to form a lens, to produce a ray bundle convergent upon the sensitive part of the crystal or the like. Various further features will be described for the promotion of improved electric connections and for the enhanced resistivity to mechanical shock.

In Figs. Ito 3 of the drawings, my invention is shown in application to a single-element cell, which may employ a radiation-responsive eleadhesive allowed to set.

ment in the form of a single crystal [0. The crystal I 0 may be of cadmium sulphide or zinc sulphide, or of the selenides of such metals. The crystal It may thus comprise an elongated prismatic element having parallel opposed faces II-l2 with electric-contact portions 13-44 at spaced locations thereon. In the form shown, the contact portions i3l4 are at the ends of the crystal l0, and their extent determines or limits the sensitive area between these ends.

In accordance with a feature of the invention, electrical contact to the contact areas i3-ld is made by a plurality of relatively rigid terminal members i5-l6 having enlarged heads ll--IB for large-area contact with and support of the contact portions 13-44 of the crystal Ill. The terminal members l5-l6 may be locally weakened, as at 22, for a purpose to be made clear. During assembly the heads Ill-48 may be temporarily secured to the contact portions iS-M on, the underface 12 of the crystal, as by means of a suitable adhesive; thereafter, a coating of electrically conducting material may be applied to overlap parts of the terminal members l5i6 and of the electric-contact portions l3-M. The coating it may be of a commercially available material, such as Aquadag, and I prefer that the coating shall entirely overlap all parts of the crystal except the intermediate portion which is to remain radiation-responsive. The coating 19 also preferably overlaps the entire exposed portion of the heads li--l8.

In the alternative construction of Fig. l, a permanent electrically conducting relation is further promoted by employment of flexible wires 20 coiled and preferably welded at 2! to the terminal members [5-46 (preferably between the heads i'i-lil and weakened portions 22) and cemented at the other ends to other parts of the electric-contact portions l3i l. The conductive coating may then additionally overlap part of the wires 2t, as indicated at E9.

In assembling the device, clamping means 23 may first hold the terminal members in desired spatial relation, with the faces of heads lll8 aligned in the same plane. Adhesive may then be applied to these faces or to the electric-contact parts or element Iii, after which the element it is pressed against the heads lli8 and the Electrical contact is then enhanced by applying the conductive coatings it, with or without wires 2t, as dictated by specific application requirements. The clamped assembly may then be inverted over an open die or mold 25, which may be contoured to the desired final cell shape. In the form shown in Fig. 2, this shape is generally cylindrical, with a lens-forming contour at the end 25; the plastic forming the cell body may be of a transparent insulating material known to the trade as Kelon, which may be simply poured into the mold, to a depth to cover the weakened portions 22.

In setting the clamp- 23 on members l |'6,. and in elevating clamp- 23 on the rim of the die- 24, care should be taken to position the radiation-sensitive area II of element so as to assure interception of converging rays from the lens shape 26. I prefer that the area shall be symmetrical about the cptie-.-axis-.of.lens=-26 and. substantially at the focus thereof.

Fig. 5 illustrates an alternative method of casting for cells to be finished with aflat end face adjacent the sensitive area of 'element'lo'. The terminal members may be frictionally held" in rubber-like bushings 21, fitted in holes 28 in a base plate 29, so that the assembly l0-l5|6 (including weakened portions 22) may project upwardly into the bore 30 of a topdie plate. 31;. alternatively, the bushings 2.1 may be replaced with soap or like packing to provide the desired. temporary frictional support. In casting, the insulating transparent plastic may fill the bore 39 to excess, so that after the plastic has set the top face may be ground and polished flat, as at the section suggested bythe dottedv line 32-. The completed cell may be removedby parting the die plates 29--3i to expose the cell body,.and. by then grasping the cell body to remove the terminal members l5-I6 from the lower plate 29.

It will be seen. that I havedisclosed an improved cell construction and method of construction, featuring mechanical ruggedness and enhanced energy-gathering properties. My construction lends itself toquantity production, as by employing elongated clamps 23 to support terminal members-for a plurality of cells, or by providing multiple molds in the same dieplate. The weakened portions 18, cast within the cell body, serve to anchor the terminal .members l5--I6 and toprevent twisting of the lead wires within the plastic, thus preserving electrical.

continuity.

While I have described theinvention for the preferred forms shown, it will be understood that modifications may be made within the scope of the invention as defined in the claims which follow.

I claim:

1. In a cell construction ofthe character indicated, an elongated crystalline element electrically responsive to radiation, electric-contact portions at longitudinally spaced locations on one surface of said element, relatively rigid terminal members each including an enlarged supporting head at one end thereof, said heads being rigidly secured to said element at different of said electric-contact portions'and in electrically conducting relation therewith, and a body of plastic material transparent to radiation and completely encasing said element and parts of said terminal members near said ends thereof, each said terminal member including a locally weakened mechanical-shock-resistant portion spaced from said contact portions and encased by said plastic material.

2. In a cell construction of the character indicated, an elongated prismatic crystal electri- 4 cally responsive to radiation and including terminal portions at opposite ends thereof, means shielding said ends against electrical response to radiation, whereby the portion intermediate said ends may be thus responsive, two terminal members each including a flattened relatively large area head at one end thereof, said heads being secured to the terminal" portions of said: crystal in electrically conductingrelation therewith, and a body of plastic insulating material transparent to radiation and completely encasing said element and parts of said terminal members near said ends thereof, each said terminal member including. alocally weakened portion spaced .fromsaid crystal and contained within said body.

.3 .91. construction according to claim 2, in which said enlargedsupporting heads are formed integrally with said terminal members.

4. A construction according to claim 2, in which said terminal members are of relatively rigid wire with said, heads being formed. as flattened upset ends thereof.

5. A construction according to. claim ,2, in which a conductive coating overlaps parts of said headsand of said. crystal ends.

6. A. construction according to claim 2, in which a relatively flexible conducting member is secured to one of said terminal members and to the corresponding crystal. end independently of the terminal-head connection. to said end.

'7. A construction according to claim 6, in which a conductive coating overlaps parts .of said flexible member and of said crystal and and of said one terminal member.

8. In a cell construction of the character indicated. a cell body including a convex outer surface in an insulating material transparent to radiation, a radiation-responsive element. including a sensitive area intimately bonded to said material within said body and facing said surface, and electrical leads to said element on opposite sides of said area, said leads including locally weakened portions spaced from said element and fully contained within .and intimately supported by said body.

9. In an electrical cell of the character indicated, an elongated prismatic crystal electrically responsive to radiation, two relatively rigid elongated lead members rigidly secured to spaced parts of said crystal, said lead members including locally reduced and thus weakened portions intermediate said crystal and the remote ends of said lead members, and a single radiationtransparent body intimately encasing said crystal and said lead members at least to said weak ened portions, with the remote ends of said lead members. projecting externally of said body.

CHARLES EKSTEIN.

Touceda et a1. Nov. 26, 1940 Burke Feb. 19, 1952 OTHER REFERENCES Plastic-Imbedded Circuits, by Cumming in Electronics, June 1950, pp. 66-69.

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